An ALMA survey of CO in submillimetre galaxies: companions, triggering, and the environment in blended sources. Issue 3 (14th June 2018)

• Record Type: Journal Article
• Authors: Wardlow, J L; Simpson, J M; Smail, Ian; Swinbank, A M; Blain, A W; Brandt, W N; Chapman, S C; Chen, Chian-Chou; Cooke, E A; Dannerbauer, H; Gullberg, B; Hodge, J A; Ivison, R J; Knudsen, K K; Scott, Douglas; Thomson, A P; Weiß, A; van der Werf, P P
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 479:Issue 3(2018)
• Page Start: 3879
• Page End: 3891
• Publication Date: 2018-06-14
• Subjects: galaxies: evolution -- galaxies: ISM -- submillimetre: galaxies; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/sty1526
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: We present ALMA observations of the mid-J 12 CO emission from six single-dish selected 870-μm sources in the Extended Chandra Deep Field-South and UKIDSS Ultra-Deep Survey fields. These six single-dish submillimetre sources were selected based on previous ALMA continuum observations, which showed that each comprised a blend of emission from two or more individual submillimetre galaxies (SMGs), separated on 5–10 arcsec scales. The six single-dish submillimetre sources targeted correspond to a total of 14 individual SMGs, of which seven have previously measured robust optical/near-infrared spectroscopic redshifts, which were used to tune our ALMA observations. We detect CO(3–2) or CO(4–3) at z = 2.3–3.7 in 7 of the 14 SMGs, and in addition serendipitously detect line emission from three gas-rich companion galaxies, as well as identify four new 3.3 mm selected continuum sources in the six fields. Joint analysis of our CO spectroscopy and existing data suggests that $64(\pm 18){{\rm \, per\, cent}}$ of the SMGs in blended submillimetre sources are unlikely to be physically associated. However, three of the SMG fields (50 per cent) contain new, serendipitously detected CO-emitting (but submillimetre-faint) sources at similar redshifts to the 870 μm selected SMGs we targeted. These data suggest that the SMGs inhabit overdense regions, but that these are not sufficiently overdense on ∼100 kpc scales to influence the source blending given the short lifetimes of SMGs. We find that $21\pm 12{{\rm \, per\, cent}}$ of SMGs have spatially distinct and kinematically close companion galaxies (∼8–150 kpc and ≲ 300 km s −1 ), which may have enhanced their star formation via gravitational interactions.